Junction structure

A junction structure comprising:

• a first material that is a metallic material, and a third material that is a metallic material and is weldable to the first material, at least one of the first material or the third material having:
• a weld zone where the first material and the third material are melted and joined together;
• and
• at least one exhaust groove or at least one exhaust hole around the weld zone, the at least one exhaust groove or the at least one exhaust hole penetrating a thickness of the at least one of the first material or the third material;
• and
• a second material which is a nonferrous metallic material or a nonmetallic material, the second material being sandwiched and fixed between the first material and the third material by lap joining,
• wherein:
• the second material has a through part;
• the at least one of the first material or the third material has a projection;
• the projection is located in the through part;
• and
• the at least one exhaust groove or the at least one exhaust hole is located outside the projection and is either:
• (i) located at least partially inside an inner periphery of the through part;
• or (ii) aligned with the inner periphery of the through part.